Apart from the frequently used liquid fuels, the use of gaseous fuels, such as natural gas or hydrogen, has been increasing over the past few years. However, the known injectors for liquid fuels are only conditionally suitable for such gaseous fuels, since gaseous fuels have different energy densities and volumes than liquid fuels. To ensure that internal combustion engines operated in this manner do not consume too much fuel, it is necessary to inject the most precise gas quantities possible in each injection. In the future, to save fuel, it will also be necessary to handle one or more injection process(es) per combustion cycle. Apart from the requirement of injecting a certain maximum quantity within a predefined period of time, it must also be possible to meter defined minimal gas quantities in a precise manner. The gas injector also needs to seal with respect to the combustion chamber between different injections. FIG. 1 schematically illustrates an example of a known gas injector, in which an outwardly opening valve needle 3 sits on a valve seat 2 inside a housing 5. FIG. 1 shows the closed state of the injector. FIG. 2 schematically shows a diagram of a characteristic of the effective overall opening cross-section A across lift H. Here, a linear characteristic comes about both for smaller lifts and for large lifts H, as long as the released annular cross-sectional area at the valve needle constitutes the smallest cross-section. A constant cross-sectional area Amax, which is independent of lift H, therefore results as soon as the annular gap between nozzle needle 3 having radius R1 and the outer contour (radius R3 at valve seat 2) of the gas supply of the injector constitutes the smallest cross-section. For this reason the curve in the diagram of FIG. 2 is horizontal up to maximum lift Hmax in the end region.
A conflict in goals between the metering of minimal quantities and a maximally desired quantity per injection cycle exists in the configuration of gas injectors. Because of the relatively low density of gaseous fuels, great volumes must be injected within a short period of time at space requirements that are comparable to an injector for liquid fuels. To do so, a gas injector should be able to release large cross-sections as rapidly as possible at a given lift. The concept of the gas injector shown in FIGS. 1 and 2 has the steepest possible cross-sectional characteristic across the lift. However, this makes it difficult to meter minimal quantities, and multiple injections, in particular, are impossible to realize.